This application claims the priority of German Patent Document No. 101 07 875.7, filed Feb. 20, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a system and a method for cooling a fuel cell arrangement using a coolant circuit, particularly a fuel cell arrangement having a gas generating system used in a motor vehicle.
German Patent Document DE43 27 261 C1 discloses a cooling system which has a separate coolant circuit for each assembly. The separate coolant circuits are coupled by way of a heat exchanger for heating the vehicle occupant compartment of a vehicle.
However, this cooling system has the disadvantage that each of the separate coolant circuits must have all the devices of a coolant circuit, such as the coolant delivery device, the filter and the like. The costs associated with the components and the space requirement of the cooling system are therefore considerably increased.
European Patent Document EP0 842 548 B1 discloses a cooling system which is used particularly for cooling a fuel cell arrangement. To improve the cold-starting behavior of the fuel cell system or fuel cell arrangement, this cooling system has a bypass line around a cooler, which bypass line can be controlled by a valve device. As a result, the coolant circuit can be operated completely or partially without the actual cooler which results in a very rapid heating of the coolant circulating in the coolant circuit.
Japanese Patent Document JP09320626 A discloses a construction similar to that of the cooling system according to the above-mentioned European patent document. Japanese patent document also shows a bypass line around a cooler or heat exchanger which can be blocked by a valve controllable as a function of a temperature.
However, these two constructions have the disadvantage that, although they are suitable for a very rapid heating of the entire coolant circuit, only one temperature level can exist in the entire coolant circuit because all components to be cooled are supplied with the coolant at this temperature level.
It is an object of the present invention to provide a system for cooling a fuel cell arrangement, particularly a fuel cell arrangement with a gas generating system used in a motor vehicle, which is capable of supplying different components in a coolant circuit with coolant at different temperature levels.
The solution according to the invention provides at least two valve devices in the coolant circuit. Each of the valve devices can adjust the rate of flow as a function of the temperature in a region assigned to a component. Further, each of the valve devices is assigned to one of the components to be cooled, or to a group of components which are to be cooled at the same time in the operation of the fuel cell arrangement to the same or a similar temperature level, by means of a coolant circuit. As a result, different temperature levels can be achieved.
This results in the advantage that, for example, the fuel cell, at the start of the operation of the fuel cell arrangement, is cooled to a much higher temperature than the other components and auxiliary aggregates, such as electronic components, motors, pumps, or the like. The fuel cell requires a comparatively long time after the start of the fuel cell arrangement to reach the ideal operating temperature. The other components and auxiliary aggregates require the full cooling capacity at the start of operation.
In a preferred embodiment of the invention, the coolant circuit has a bypass line around each of the cooler and a component to be cooled. The valve devices can adjust the ratio of the rates of flow through the cooler or the component and through the respective bypass line.
Thus, by adjusting the ratio of the flow rates through the component to be cooled or the cooler and the respective bypass line, the temperature level in the coolant circuit can be effectively and easily controlled or regulated virtually independently. By adjusting the bypass of the component to be cooled, the temperature level in this component can be controlled or regulated independently of the remainder of the coolant circuit.
In this case, it is naturally not possible to lower the temperature level in this region, but the conventional application also provides that the corresponding components, for example, in the starting phase of the fuel cell arrangement, do not require the same high cooling capacity as in their regular operation.
Thus, by way of the first of the valve devices and the bypass line around the cooler, a basic temperature level can be adjusted for the entire coolant circuit. By way of the second valve device and the bypass line around the component to be cooled, such as the fuel cell, a higher temperature level can be adjusted. Thus, after the fuel cell arrangement is started, an ideal cooling of all components to the temperature level ideal at this time can be achieved very rapidly. A demand-oriented cooling of the respective components at any time is therefore permitted in a particularly advantageous manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.